Oldest star provides hints about first supernovas

The first stars in the universe, illustrated here, may not have died in the explosive fireworks of those today. That could be why second-generation stars, the most ancient ones astronomers can still study, have very little iron.

Studying one of the oldest known stars in the universe has given astronomers a closer look at what happened in the universe more than 13.7 billion years ago.

Named SMSS J031300.362670839.3, the star sits 6,000 light-years from Earth toward the outskirts of the Milky Way and lacks iron. Scientists thought that the high-energy explosions, or supernovas, of the universe's first stars would have seeded galaxies with this heavy element. But the old star’s chemical composition and that of four others suggest that the explosions of the first stars were much lower in energy than those of giant stars today.

Any iron formed in those earliest explosions probably fell into the resulting black hole. That could explain why old, second generation stars such as SMSS J031300.362670839.3 have very small traces of iron, and it suggests that low-energy supernovas were more common in the early universe than originally thought, astronomers report February 9 in Nature.